Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already establish read-only, idempotent, non-destructive, open-world behavior. The description adds useful context beyond that: it returns only the requested article's caption, heading, and text rather than the whole law, and as_of retrieves the text as it stood on a given date.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with purpose and scope, then examples, then the sibling-tool distinction, then historical lookup. Every sentence contributes useful selection or invocation information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only single-article fetch with full schema coverage and annotations, the description is complete enough: it names the return fields, explains the filtering scope, documents historical behavior, and identifies the data source.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds meaningful semantics: it shows a real law_id example with the statute name and explains that branch forms like 27条の2, 27-2, 27_2, and kanji resolve to the same normalized article. The as_of behavior is also clarified beyond the schema wording.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource: fetch a single article of a Japanese law by law id and article number. It gives concrete examples, explains branch-article resolution, and explicitly distinguishes this from get_law when the article is known.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly says to use this instead of get_law when you know the article you want, and it documents multiple accepted article-number formats. The as_of parameter's purpose for historical amendment states is also clearly framed.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.